The invention relates to the field of optical communications systems, and particularly to optical fiber switching by means of a device arranged for precise alignment of one optical fiber into another optical fiber and preferably operated by electro-magnetic means.
Fiber optics telecommunications lines are being installed world wide to provide higher bandwidth and greater reliability than copper wire lines, microwave relay stations or satellites. A fiber optic communications system includes switching stations so that communications signals may be routed between any two locations in the network. Each switching station switches signals carried by one optical fiber to a selected one of a plurality of optical fibers for transmission to another switching station in the network. Systems for switching optical signals between optical fibers include an apparatus to place the fibers end-to-end so that light may be coupled out of one fiber into another. One drawback with fiber optic communications systems is that the switches used to make and break connections are expensive and unreliable.
The switching station should be highly reliable and have low insertion loss and low back reflections. Insertion loss reduces signal strength whereas reflected signals cause cross talk. The fiber ends must be axially and laterally aligned and must be spaced apart by only a very small distance to meet the operational requirements.
Some designs use elaborate structures to solve alignment problems. In U.S. Pat. No. 4,189,206, for example an optical fiber is guided into a slit formed between two contact poles and through a guide hole formed by two bars transversely attached to one end of the contact poles. Another prior art switching apparatus in U.S. Pat. No. 6,044,186 issued to Chang et al. connects a first optical fiber with a switching member that is arranged to be pivoted between a first position and a second position. The ends of the first and second optical fibers are placed to be in alignment when the switching member is in its first position and out of position when the switching member is in its second position. The drawback of the learned art is that the first optical fiber is connected with the switching member so that alignment between the first and second fibers is very likely influenced by the first optical fiber and the switching member due to the connection of the first optical fiber and the switching member and the mechanic error associated with the switching member. Thus the ideal use of repeatability can hardly be obtained.
The present invention provides a better solution to the problems described above and is liable to overcome the disadvantages of the learned art.
The present invention overcomes the problems associated with the prior art described above by providing a highly reliable fiber optic switching apparatus that requires no lenses or stepping motors. It is also provided a fiber optic switching apparatus with high switching speed, low power consumption, small size and a wide operating temperature range. According to the present invention, the optical fibers in a fiber optic switching apparatus will not vibrate with the switching member when they are in alignment. The present invention further covers an anti-reflection coating (ARC) on the end surface of the optical fibers in the fiber optic switching apparatus to avoid Fabry-Perot effect, thereby rendering the insertion loss spectrum between the optical fibers flattened and the insertion loss and reflection of the optical coupling between the optical fibers reduced.
According to the present invention, a fiber optic switching apparatus comprises a fiber alignment head having a groove formed therein to mount with a first optical fiber and a second optical fiber that is arranged with its end adjacent to a switching member pivotable between a first position and a second position. The ends of the first and second optical fibers are in alignment in the groove of the fiber alignment head when the switching member is in its first position. When the switching member is in its second position, it pushes the second optical fiber upward so that the ends of the first and second optical fibers are out of alignment. The improvement is that the second optical fiber is secured in the fiber optic switching apparatus with a means that is detached from the switching member. As a result, the end of the second optical fiber does not vibrate with the switching member when the optical fibers are placed end-to-end in alignment in the groove of the fiber alignment head.
The second optical fiber, the means for supporting the second optical fiber and the groove are preferably arranged such that when the switching member is in its first position, the end of the second optical fiber is bent so that elastic forces retain it in alignment with the end of the first optical fiber in the groove.
It preferably comprises an electromechanical relay that comprises a housing apparatus for pivotally mounting the switching member in the housing and an apparatus arranged to latch the switching member such that the first and second optical fiber ends are selectively either in or out of alignment.
The ends of the first and second optical fiber are preferably formed with a cleaved surface at an angle and an anti-reflection coating (ARC) is covered onto the cleaved surface.
According to the present invention, a fiber optic switching apparatus further comprises a second fiber alignment head with a second groove formed therein for mounting a third optical fiber. The two grooves of the first and second fiber alignment heads are mounted in facing relationship so that the end of the second optical fiber is in alignment with the end of the third optical fiber in the second groove when the switching member is in its second position.